In the case of such a piston which is known from U.S. Pat. No. 4,180,027, one problem is that of evenly cooling the piston head over its entire periphery. As a rule, the cooling of the piston head is more intensive in the area in which the cooling oil is injected than it is in the areas remote from the cooling oil injection point. For this reason, it is already known from JP-A 56-124650 to enlarge the cooling oil space or the piston head with increasing remoteness from the injection point. This is likewise desired in the case of the piston mentioned at the outset.
To this end, it would be necessary to enlarge the annular cooling oil space at that point where it is quite remote from the point at which the cooling oil is injected. In the case of so-called articulating pistons which are articulatingly assembled from an upper piston part and a stem part, however, this requirement cannot be readily met, since the space required for the bosses, and which has to be kept clear when the piston is mounted in its stem part, makes it impossible to enlarge the cooling oil space.